Shakey Gauge

[Tohm]

I've got shakey gauges.

Just purchased my first square body (85 c10). The speedometer and gas gauge work, but kind of barely. They jump and shake a lot. Speedo moves plus or minus 10 mph and the gas gauge kind of just does what it wants. The other gauges work fine which leads me to believe I've got grounding issue for the two main gauges. Anyone have a similar issue? Obvious things to check before removing the gauge cluster and sending unit?

 

[dsteelejr]

The speedometer is a mechanical gauge driven by a cable that plugs into the tail housing of the transmission or transfer case. There is nothing electrical with the speedometer. It’s not uncommon for the the speedometer needle to bounce around. The cable is binding up. Disconnect the cable at the gauge and squirt some oil into the cable. If that doesn’t help you can replace the cable. They’re not that expensive.

 

[squaredeal91]

Oil speedo cable and back of speedometer. I bet if you listen closely you can hear the speedometer whine. I've had to lube mine up because of this.

 

[squaredeal91]

Your fuel gauge is something different. They move around when the truck does. It's resistor There's a resistor you can add to stop that. Some of the trucks didn't have this problem but there's many pages on here about the fuel gauge movement specifically.

 

[dsteelejr]

Check the ground on your fuel sending unit. There’s a positive pink wire running from the bulkhead connector on the firewall under the hood that runs to the fuel sender on the tank. The ground is a short black wire with a ring connector and bolts to frame. That connection gets corroded with time. All the dirt, grime, road salt, etc causes a bad ground connection.

 

[75gmck25]

Once you find the sending unit ground on the side of the frame rail, you will understand how it gets corroded and makes a bad connection. It’s fully exposed to road dirt, oil, etc. Remove the bolt, sand the frame and wire connector down to bare metal, and screw everything back down tightly.

The power wire connection at the top of the sending unit should have a socket with a rubber boot that pushes onto the sending unit positive post, but that boot also takes a beating.

 

[wanderinthru]

Hey, what you doing with my gauges?

 

[Snoots]

There's also a ground just north of the parking brake pedal on the kick panel. Take it off and clean everything. Smear a dab of copper anti-seize on the connections before re-installing. You'll be glad you did.

Shakey puddin' is better than shaky gauges!